US20170272050A1 - Resonator manufacturing method - Google Patents
Resonator manufacturing method Download PDFInfo
- Publication number
- US20170272050A1 US20170272050A1 US15/610,896 US201715610896A US2017272050A1 US 20170272050 A1 US20170272050 A1 US 20170272050A1 US 201715610896 A US201715610896 A US 201715610896A US 2017272050 A1 US2017272050 A1 US 2017272050A1
- Authority
- US
- United States
- Prior art keywords
- wafer
- resonator
- thickness
- degenerated
- manufacturing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 42
- 239000012535 impurity Substances 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 43
- 239000010408 film Substances 0.000 claims description 91
- 238000009826 distribution Methods 0.000 claims description 68
- 239000010409 thin film Substances 0.000 claims description 63
- 238000009966 trimming Methods 0.000 claims description 3
- 235000012431 wafers Nutrition 0.000 description 106
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 34
- 230000010355 oscillation Effects 0.000 description 32
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 30
- 239000000758 substrate Substances 0.000 description 29
- 230000002093 peripheral effect Effects 0.000 description 15
- 239000000377 silicon dioxide Substances 0.000 description 15
- 229910052681 coesite Inorganic materials 0.000 description 14
- 229910052906 cristobalite Inorganic materials 0.000 description 14
- 229910052682 stishovite Inorganic materials 0.000 description 14
- 229910052905 tridymite Inorganic materials 0.000 description 14
- 238000010586 diagram Methods 0.000 description 9
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 239000002019 doping agent Substances 0.000 description 5
- 238000005304 joining Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 4
- 238000005530 etching Methods 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 229910052814 silicon oxide Inorganic materials 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 229910002601 GaN Inorganic materials 0.000 description 2
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 2
- 229910018503 SF6 Inorganic materials 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 229910052787 antimony Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 229910052785 arsenic Inorganic materials 0.000 description 2
- NWAIGJYBQQYSPW-UHFFFAOYSA-N azanylidyneindigane Chemical compound [In]#N NWAIGJYBQQYSPW-UHFFFAOYSA-N 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910052732 germanium Inorganic materials 0.000 description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 2
- 238000010884 ion-beam technique Methods 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 2
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 229910052707 ruthenium Inorganic materials 0.000 description 2
- 238000001004 secondary ion mass spectrometry Methods 0.000 description 2
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 description 2
- 238000001039 wet etching Methods 0.000 description 2
- 239000011787 zinc oxide Substances 0.000 description 2
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229910003327 LiNbO3 Inorganic materials 0.000 description 1
- 229910012463 LiTaO3 Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- FYOZFGWYYZDOQH-UHFFFAOYSA-N [Mg].[Nb] Chemical compound [Mg].[Nb] FYOZFGWYYZDOQH-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 229910021419 crystalline silicon Inorganic materials 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000001312 dry etching Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- QRNPTSGPQSOPQK-UHFFFAOYSA-N magnesium zirconium Chemical compound [Mg].[Zr] QRNPTSGPQSOPQK-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
- 229910052696 pnictogen Inorganic materials 0.000 description 1
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 1
- BITYAPCSNKJESK-UHFFFAOYSA-N potassiosodium Chemical compound [Na].[K] BITYAPCSNKJESK-UHFFFAOYSA-N 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229960000909 sulfur hexafluoride Drugs 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052984 zinc sulfide Inorganic materials 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/0072—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks of microelectro-mechanical resonators or networks
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02086—Means for compensation or elimination of undesirable effects
- H03H9/02102—Means for compensation or elimination of undesirable effects of temperature influence
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
- B81B3/0064—Constitution or structural means for improving or controlling the physical properties of a device
- B81B3/0081—Thermal properties
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/0072—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks of microelectro-mechanical resonators or networks
- H03H3/0076—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks of microelectro-mechanical resonators or networks for obtaining desired frequency or temperature coefficients
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02244—Details of microelectro-mechanical resonators
- H03H9/02259—Driving or detection means
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/24—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
- H03H9/2405—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive of microelectro-mechanical resonators
- H03H9/2447—Beam resonators
- H03H9/2463—Clamped-clamped beam resonators
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/24—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
- H03H9/2405—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive of microelectro-mechanical resonators
- H03H9/2468—Tuning fork resonators
- H03H9/2478—Single-Ended Tuning Fork resonators
- H03H9/2489—Single-Ended Tuning Fork resonators with more than two fork tines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C2201/00—Manufacture or treatment of microstructural devices or systems
- B81C2201/01—Manufacture or treatment of microstructural devices or systems in or on a substrate
- B81C2201/0174—Manufacture or treatment of microstructural devices or systems in or on a substrate for making multi-layered devices, film deposition or growing
- B81C2201/0181—Physical Vapour Deposition [PVD], i.e. evaporation, sputtering, ion plating or plasma assisted deposition, ion cluster beam technology
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02244—Details of microelectro-mechanical resonators
- H03H2009/02488—Vibration modes
- H03H2009/02496—Horizontal, i.e. parallel to the substrate plane
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/24—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
- H03H9/2405—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive of microelectro-mechanical resonators
- H03H2009/241—Bulk-mode MEMS resonators
Definitions
- the present disclosure relates to a method for manufacturing a resonator.
- resonators such as piezo-resonators
- ingots of Si silicon
- impurities such as n-type dopants like P (phosphorus)
- a plurality of wafers are cut out from these ingots, and resonators are formed in a plurality of zones defined on the wafers. Thereafter, the respective zones are cut along the outlines of the respective zones of the wafers to thereby form resonance devices.
- the ingots of Si are manufactured substantially in cylindrical shapes by the growth of single-crystalline Si according to, for example, a manufacturing method referred to as a CZ method (Czochralski method).
- the ingots are manufactured by melting, on heating, polycrystalline Si doped with large amounts of n-type dopant, for example, such as P, and immersing Si rods in the molten Si, and lifting the Si rods while rotating the rods.
- Patent Document 1 Japanese Patent Application Laid-Open No. 2010-028536.
- these ingots each have a higher impurity concentration at the outer peripheral side in a radial direction of the ingot than at the inner peripheral side therein. At the same time, these ingots also have a higher impurity concentration at the bottom side in a lifting direction of the ingot than the top side therein.
- the ingots each have a resistivity distribution formed to decrease in resistivity from the inner peripheral side toward the outer peripheral side, and a resistivity distribution formed to decrease in resistivity from the top side toward the bottom side.
- the present disclosure provides a method for manufacturing a resonator that is capable of effectively addressing the variation in resistivity for each wafer.
- a method for manufacturing a resonator includes the step of forming a Si oxide film at the surface of a degenerated Si wafer, where the Si oxide film has a thickness set in accordance with the doping amount of impurity in the Si wafer.
- a method for manufacturing a resonator includes the step of forming a piezoelectric thin film on the surface of a degenerated Si wafer, where the piezoelectric thin film has a thickness set in accordance with the distribution of the doping amount of impurity in the Si wafer in an in-plane direction of thereof.
- a wafer body includes a degenerated Si wafer; and a piezoelectric thin film formed on the surface of the Si wafer, where the piezoelectric thin film has a thickness set in accordance with the distribution of the doping amount of impurity in the Si wafer in an in-plane direction of thereof.
- a method for manufacturing a resonator can be provided that effectively addresses the variation in resistivity for each wafer.
- FIG. 1 is a perspective view schematically illustrating the appearance of a piezoelectric resonance device according to an exemplary aspect.
- FIG. 2 is an exploded perspective view schematically illustrating the structure of a piezoelectric resonance device according to an exemplary aspect.
- FIG. 3 is a pattern diagram of a cross section of the piezo-resonator along the line 3 - 3 of FIG. 2 .
- FIG. 4 is a graph showing the relationship between the thickness of a Si oxide film and the frequency-temperature characteristic range of a piezo-resonator.
- FIG. 5 is a graph showing the relationship between the thickness of a piezoelectric thin film and the frequency-temperature characteristic range of a piezo-resonator.
- FIG. 6 is a graph showing the relationship between the doping amount of impurity and the primary temperature coefficient of elastic constant of a piezo-resonator.
- FIGS. 7( a ) to 7( c ) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect.
- FIGS. 8( a ) to 8( c ) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect.
- FIGS. 9( a ) and 9( b ) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect.
- FIG. 10 is a graph showing the relationship between the resistivity of a wafer and the frequency-temperature characteristic range of a piezo-resonator.
- FIGS. 11( a ) to 11( c ) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect.
- FIG. 12 is an exploded perspective view schematically illustrating the structure of a piezoelectric resonance device according to another exemplary aspect.
- FIG. 13 is a pattern diagram of a cross section of the piezo-resonator along the line 12 - 12 of FIG. 12 .
- FIG. 1 is a perspective view schematically illustrating the appearance of a piezoelectric resonance device 10 according to a specific example.
- the piezoelectric resonance device 10 includes a lower substrate 11 , an upper substrate 12 that forms an oscillation space with the lower substrate 11 , and a piezo-resonator 13 sandwiched between the lower substrate 11 and the upper substrate 12 .
- the piezo-resonator 13 is a MEMS resonator manufactured by a MEMS technology that functions as, for example, a timing device incorporated in an electronic device such as a smartphone.
- FIG. 2 is an exploded perspective view schematically illustrating the structure of a piezoelectric resonance device 10 according to a specific example.
- the piezo-resonator 13 includes: a support frame 14 that spreads in the form of a rectangular frame along the XY plane in the orthogonal coordinate system in FIG. 2 ; a base 15 that spreads in the form of a flat plate along the XY plane in the support frame 14 from one end of the support frame 14 ; and a plurality of oscillation arms 16 that each extend along the XY plane from a fixed end connected to one end of the base 15 toward a free end.
- the four oscillation arms 16 extend parallel to the Y axis. It is noted that the number of oscillation arms 16 is not limited to 4, and can be, for example, any number of 3 or more according to alternative aspects.
- the lower substrate 11 spreads in the form of a plate along the XY plane, and the upper surface of the substrate has a depression 17 formed therein.
- the depression 17 formed in, for example, a flat cuboid shape forms a part of the oscillation space for the oscillation arms 16 .
- the upper substrate 12 spreads in the form of a plate along the XY plane, and the lower surface of the substrate has a depression 18 formed therein.
- the depression 18 formed in, for example, a flat cuboid shape forms a part of the oscillation space for the oscillation arms 16 .
- the lower substrate 11 and the upper substrate 12 are both formed from Si (silicon).
- the support frame 14 of the piezo-resonator 13 is received on a peripheral edge of the upper surface of the lower substrate 11 , which is defined outside the depression 17 , and a periphery of the lower surface of the upper substrate 12 , which is defined outside the depression 18 , is received on the support frame 14 of the piezo-resonator 13 .
- the piezo-resonator 13 is held between the lower substrate 11 and the upper substrate 12 , and the lower substrate 11 , the upper substrate 12 , and the support frame 14 of the piezo-resonator 13 form the oscillation space for the oscillation arms 16 .
- This oscillation space is kept airtight, and the vacuum state is maintained.
- FIG. 3 is a pattern diagram of a cross section of the piezo-resonator 13 along the line 3 - 3 of FIG. 2 .
- the oscillation arms 16 each includes: a Si oxide film (thermal oxidation film), for example, a SiO 2 layer (silicon dioxide) 21 ; an active layer, that is, a Si layer 22 laminated on the SiO 2 layer 21 ; a piezoelectric thin film, that is, an AlN (aluminum nitride) layer 23 laminated on the Si layer 22 ; a lower electrode, that is, a Mo (molybdenum) layer 24 and an upper electrode, that is, a Mo layer 25 formed on the upper surface and lower surface of the AlN layer 23 to sandwich the AlN layer 23 ; and further, an AlN layer 23 ′ laminated on the Mo layer 25 .
- the SiO 2 layer 21 may be formed between the Si layer 22 and the Mo layer 24 , or on the upper surface of the Mo layer 25 .
- a silicon oxide material including any composition of Si a O b layer (a and b are integers) is used for the Si oxide film.
- the active layer formed from a degenerated n-type Si semiconductor contains, as an impurity, that is, an n-type dopant, a Group 15 element such as P (phosphorus), As (arsenic), and Sb (antimony). It is noted that two or more of P, As, and Sb may be mixed in the active layer.
- Ge (germanium) that has a larger ionic radius than the ionic radius of Si may be added to the active layer to control lattice distortion due to impurity doping in large amounts.
- the Si layer 22 is doped with a predetermined doping amount of P (phosphorus) as an n-type dopant.
- the AlN layer 23 is a piezoelectric thin film that converts an applied voltage to oscillations.
- a ScAlN (scandium-containing aluminum nitride) layer may be used for the piezoelectric thin film.
- a MgNbAlN (magnesium-niobium-containing aluminum nitride) layer, a MgZrAlN (magnesium-zirconium-containing aluminum nitride) layer, BAlN (boron-containing aluminum nitride), and GeAlN (germanium-containing aluminum nitride) may be used for the piezoelectric thin film.
- GaN gallium nitride
- InN indium nitride
- ZnO zinc oxide
- PZT lead zirconate titanate
- KNN potassium nickel
- LiTaO 3 lithium tantalate
- LiNbO 3 lithium niobate
- a metal material such as Ru (ruthenium), Pt (platinum), Ti (titanium), Cr (chromium), Al (aluminum), Cu (copper), Ag (silver) or an alloy thereof is used for the lower electrode and the upper electrode.
- the Mo layer 24 and the Mo layer 25 are each connected to an alternating-current power supply (not shown) provided outside the piezoelectric resonance device 10 .
- an electrode (not shown) formed on the upper surface of the upper substrate 12 , a through silicon via (TSV) (not shown) formed in the lower substrate 11 or the upper substrate 12 , or the like is used.
- TSV through silicon via
- the AlN layer 23 ′ is, for example, a film for protecting the Mo layer 25 . It is noted that the layer formed on the Mo layer 25 is not limited to the AlN layer, but may be, for example, a film formed from an insulator.
- the AlN layer 23 has a wurtzite structure, which is C-axis oriented substantially perpendicular to the Si layer 22 .
- a voltage is applied in the C-axis direction through the Mo layer 24 and the Mo layer 25 , the AlN layer 23 is stretched in a direction substantially perpendicular to the C axis. With this stretching, the oscillation arms 16 undergo flexural displacement in the Z-axis direction to cause free ends thereof to undergo displacement toward the inner surfaces of the lower substrate 11 and the upper substrate 12 , thereby oscillating in an out-of-plane flexural oscillation mode.
- the thicknesses of the Si oxide film and piezoelectric thin film are controlled in accordance with the doping amount of a dopant, that is, an impurity formed in an ingot in the manufacture of the ingot used for the manufacture of the piezo-resonator 13 , and the distribution of the doping amount.
- the control of the thicknesses of the Si oxide film and piezoelectric thin film can reduce variations in frequency-temperature characteristics of the piezo-resonator 13 . Accordingly, as will be described below, the piezo-resonator 13 according to an exemplary aspect, that is, the piezoelectric resonance device 10 , can be provided which has favorable temperature characteristics.
- ingots in a substantially cylindrical shape are manufactured by, for example, a CZ method (Czochralski method).
- the doping amount of an impurity for example, such as P is set to a predetermined setting.
- the ingots manufactured each have a tendency to have a higher impurity concentration at the outer peripheral side in a radial direction of the ingot than at the inner peripheral side therein, and have a higher impurity concentration at the bottom side in a lifting direction of the ingot than the top side therein. In this way, the distribution of the impurity concentration is produced in the ingots.
- This distribution of the impurity concentration roughly agrees with the distribution of resistivity.
- the ingots each have such a resistivity distribution as a decrease in resistivity from the top side toward the bottom side.
- This resistivity distribution in the lifting direction can be specified by measuring the impurity concentration at a plurality of points in the ingot manufactured.
- the resistivity distribution can be specified by measuring the impurity concentration through SIMS (secondary ion mass spectrometry) at a plurality of points at the bottom surface of a cylindrical block of ingot with ends removed from the ingot manufactured, and measuring the impurity concentration in the same way at a plurality of points at the upper surface of the cylindrical block.
- the resistivity may be actually measured at these points.
- the resistivity can be measured by, for example, a four probe method.
- the ingots each have such a resistivity distribution as a decrease in resistivity from the inner peripheral side toward the outer peripheral side.
- This resistivity distribution in the radial direction can be specified by measuring the impurity concentration at a plurality of points in the radial direction at the bottom surface and upper surface of the cylindrical block of ingot, and in consideration of the distribution of the impurity concentration in the lifting direction, calculating the distribution of the impurity concentration in the radial direction in each position in the lifting direction of the ingot.
- a plurality of Si wafers are cut out from the cylindrical block of the ingot.
- Each Si wafer has an impurity concentration, that is, a resistivity in accordance with the location in the lifting direction in the ingot, and the wafers are sorted into respective lots grouped for each predetermined resistivity range.
- This operation of sorting into the lots is repeated for each ingot, thereby collecting, for each lot, a plurality of Si wafers with resistivity in a predetermined range, which are cut from a plurality of ingots.
- the resistivity of the Si wafer as a criterion for sorting into the lots is specified on the basis of the average value for the doping amount of impurity (average value for resistivity) in the in-plane direction of the Si wafer.
- the thickness of the Si oxide film, that is, the SiO 2 layer 21 formed at the Si wafer is controlled, for example, in each lot unit.
- the frequency-temperature characteristic range of the piezo-resonator 13 can be controlled appropriately in accordance with the distribution of the doping amount of impurity (resistivity) in the ingot in the lifting direction.
- FIG. 4 is a graph showing the relationship between the thickness of the Si oxide film and the frequency-temperature characteristic range of the piezo-resonator 13 .
- the frequency-temperature characteristic range [ppm] refers to a value indicating a difference, that is, a magnitude of change between the maximum value and minimum value of the frequency in the operation temperature range (for example, ⁇ 40° C. to 85° C.) of the piezoelectric resonator 13 . As this frequency-temperature characteristic range is smaller, the variation in frequency-temperature characteristics is reduced.
- the thickness of the piezoelectric thin film that is, the AlN film 23 may be controlled.
- the thickness of the AlN film 23 is controlled in each lot unit.
- the frequency-temperature characteristic range of the piezo-resonator 13 can be controlled appropriately in accordance with the distribution of the doping amount of impurity (resistivity) in the ingot in a radial direction.
- FIG. 5 is a graph showing the relationship between the thickness of the piezoelectric thin film and the frequency-temperature characteristic range of the piezo-resonator 13 .
- the frequency-temperature characteristic range [ppm] refers to a value indicating a difference, that is, a magnitude of change between the maximum value and minimum value of the frequency in the operation temperature range (for example, ⁇ 40° C. to 85° C.) of the piezoelectric resonator 13 .
- the doping amount of impurity is 1.26 ⁇ 10 20 atm/cm 3 near the center of the Si wafer, whereas the doping amount of impurity is 1.30 ⁇ 10 20 atm/cm 3 near the outer periphery of the Si wafer.
- the thickness of the piezoelectric thin film is set to 0.850 ⁇ m with which the frequency-temperature characteristic range reaches a minimum value.
- the thickness of the piezoelectric thin film is set to 0.790 ⁇ m with which the frequency-temperature characteristic range reaches a minimum value.
- the distribution of the doping amount of impurity is formed in the in-plane direction of the Si wafer, and the thickness distribution is thus set in the radial direction in the case of the AlN film 23 in accordance with the distribution of the doping amount, formed in the radial direction from the inner peripheral side of the Si wafer toward the outer peripheral side thereof, for example.
- This thickness distribution of the piezoelectric thin film in the radial direction is set so as to achieve a thickness distribution in which the frequency-temperature characteristic range reaches a minimum value, thereby reducing the variation in frequency-temperature characteristics.
- FIG. 6 is a graph showing the relationship between the doping amount of impurity and the primary temperature coefficient of elastic constant of the piezo-resonator 13 .
- the frequency-temperature characteristics increase in a relatively rapid manner up to approximately 9 ⁇ 10 19 atm/cm 3 as the doping amount of impurity in the Si wafer is increased from 0, while the frequency-temperature characteristics decrease in relatively gradual manner when the doping amount of impurity exceeds approximately 9 ⁇ 10 19 atm/cm 3 .
- the doping amount (resistivity) in the in-plane direction of the Si wafer for example, a material such as AlN or ScAlN that has a negative primary temperature coefficient of elastic constant is used as the piezoelectric thin film, and when the doping amount in the Si wafer is more than approximately 9 ⁇ 10 19 atm/cm 3 , the thickness of the piezoelectric thin film is increased at the outer peripheral side of the Si wafer, rather than at the inner peripheral side thereof. On the other hand, in the case of the doping amount below approximately 9 ⁇ 10 19 atm/cm 3 , the thickness of the piezoelectric thin film is decreased at the outer peripheral side of the Si wafer, rather than at the inner peripheral side thereof. More specifically, it is preferable to control the thickness distribution of the piezoelectric thin film, with the doping amount of approximately 9 ⁇ 10 19 atm/cm 3 as a threshold value.
- the distribution of the doping amount (resistivity) in the in-plane direction of the Si wafer can be also addressed by control of the thickness distribution of the thin film (resonator-constituting thin film) constituting the piezo-resonator 13 formed above the Si layer 22 , in place of the control of the thickness distribution of the piezoelectric thin film.
- the resonator-constituting thin film include, for example, the lower electrode 24 and the upper electrode 25 .
- the distribution of the doping amount (resistivity) in the in-plane direction of the Si wafer can be also addressed by control of the distribution of, for example, the thickness of a parasitic capacitance-reducing (for example, silicon oxide) layer formed between the lower electrode 24 and the Si layer 22 , or the thickness of an additional thin film layer such as a protective film layer of, for example, a silicon oxide layer or an AlN layer formed on the upper electrode 25 .
- a parasitic capacitance-reducing for example, silicon oxide
- an additional thin film layer such as a protective film layer of, for example, a silicon oxide layer or an AlN layer formed on the upper electrode 25 .
- the thickness distribution of the resonator-constituting thin film in the case of using, as the resonator-constituting thin film, a material such as, for example, AlN, Mo, Al, Pt, Ru, Ir (iridium), Ti, ScAlN, or SiN (silicon nitride) that has a negative primary temperature coefficient of elastic constant, it is preferable to control the thickness distribution of the resonator-constituting thin film, with the doping amount of approximately 9 ⁇ 10 19 atm/cm 3 as a threshold value in the same way as described previously. The distribution of the thickness in the in-plane direction of the Si wafer is controlled in the same way as described previously.
- a material that has a positive primary temperature coefficient of elastic constant such as SiO 2 or SiOF (fluorine-containing silicon oxide film)
- SiO 2 or SiOF fluorine-containing silicon oxide film
- FIGS. 7( a ) to 7( c ) are each a cross-sectional view for explaining a method for manufacturing the piezoelectric resonance device 10 according to an exemplary aspect. It is noted that while a plurality of zones corresponding to respective piezoelectric resonance devices 10 are defined on a Si wafer, only one zone on the Si wafer is illustrated in the figures for the following explanation of the manufacturing method. In addition, the thicknesses of the Si oxide film and piezoelectric thin film are controlled for each lot of a plurality of collected Si wafers with a predetermined range of resistivity.
- a plate-like wafer 31 formed from Si is prepared, and the entire surface of the wafer 31 is subjected to a thermal oxidation treatment, thereby forming a Si oxide film (for example, SiO 2 ) 32 with a predetermined thickness over the entire surface of the wafer 31 .
- a depression 33 is formed by, for example, etching.
- the wafer 31 is cleaned after removing the Si oxide film 32 . In this way, the lower substrate 11 with the depression 17 in the upper surface thereof is formed.
- a degenerated Si wafer 34 is prepared.
- the Si wafer 34 is doped with an impurity in a predetermined doping amount, the actual doping amount (resistivity) of the Si wafer 34 is specified in advance.
- the entire surface of the Si wafer 34 is subjected to a thermal oxidation treatment, thereby forming a Si oxide film (for example, SiO 2 ) 35 with a predetermined thickness.
- a thermal oxidation treatment for example, SiO 2
- TEOS oxidation films, PECVD oxidation films, and sputtered oxidation films can be used for the Si oxide film 35 .
- the thickness of the Si oxide film is set in accordance with the average value for the actual doping amount (resistivity) in the in-plane direction of the Si wafer 34 as described above.
- the lower surface of the Si wafer 34 is put on the upper surface of the wafer 31 described previously, thereby joining the Si wafer 34 to the upper surface of the wafer 31 .
- joining for example, fusion joining is carried out.
- the upper surface of the Si wafer 34 is subjected to a grinding treatment and a polishing treatment (CMP: chemical mechanical polishing), thereby grinding and removing the Si oxide film 35 at the upper surface of the Si wafer 34 and a part of the Si wafer 34 , and thus planarizing the surface of the Si wafer 34 .
- CMP chemical mechanical polishing
- a lower electrode film (for example, Mo) 36 , a piezoelectric thin film (for example, AlN) 37 , an upper electrode film (for example, Mo) 38 , and a piezoelectric thin film 37 ′ are sequentially deposited by, for example, sputtering.
- the thickness of the piezoelectric thin film 37 is set in accordance with the distribution of the doping amount of impurity (resistivity) in the in-plane direction of the Si wafer 34 as described above.
- the thickness of the piezoelectric thin film 37 has a distribution in the in-plane direction such that the thickness of the piezoelectric thin film 37 is decreased from near the center of the Si wafer 34 toward the outer periphery.
- a wafer body is manufactured which includes the piezoelectric thin film 37 with a thickness set in accordance with the distribution of the doping amount (resistivity) in the in-plane direction of the Si wafer 34 .
- an Al target (not shown) is disposed to be opposed to the upper surface of the Si wafer 34 .
- a magnet (not shown) is disposed behind the Al target to confine electrons in a magnetic field, thereby accelerating ionization of an inert gas such as Ar (argon), and thus generating a high concentration of plasma around the Al target.
- Ar argon
- the piezoelectric thin film 37 can be deposited at high speed. Accordingly, the distribution of sputtered particles that reach the upper surface of the Si wafer 34 depends largely on the distribution of the magnetic field formed by the magnet. In other words, controlling the distribution of the magnetic field allows the thickness of the piezoelectric thin film 37 to have a distribution.
- the location of the magnet or the rotation speed of the Si wafer 34 is adjusted to control the magnetic field intensity of the magnet, thereby allowing the thickness of the piezoelectric thin film 37 to have a distribution in the in-plane direction.
- the thickness of the piezoelectric thin film 37 can be controlled in a more precise manner.
- the Si wafer 34 , the Si oxide film 35 , the lower electrode film 36 , the piezoelectric thin film 37 , the upper electrode film 38 , and the piezoelectric thin film 37 ′ are subjected to, for example, dry etching or wet etching, thereby forming the shapes of the support frame 14 , base 15 , and oscillation arms 16 described above.
- the piezo-resonator 13 is formed which is supported by the support frame 14 on the upper surface of the lower substrate 11 .
- a wafer (not shown) that has depressions formed in advance in zones corresponding to the respective zones of the Si wafer 34 is joined onto the piezo-resonator 13 .
- respective piezoelectric resonance devices 10 are cut out along the outlines of the respective zones, for example, with a diamond blade or by a laser dicing method.
- the exemplary embodiments are not to be considered limited thereto, but for example, the thickness of only either the Si oxide film 35 or the piezoelectric thin film 37 may be controlled.
- the piezoelectric resonance device 10 which varies little in frequency-temperature coefficient can be provided even by controlling the thickness of only either the Si oxide film 35 or the piezoelectric thin film 37 in this way as just described.
- a method where a Si wafer is sorted into a lot on the basis of the average value for the doping amount of impurity in the in-plane direction of the Si wafer, and the thickness of the SiO 2 layer 21 formed at the Si wafer is controlled in each lot unit has been described as an example in accordance with the above-described method for manufacturing the piezoelectric resonance device 10 .
- the exemplary embodiment should not be limited thereto and it is also possible to further control the thickness of the SiO 2 layer 21 in accordance with the distribution of the doping amount of impurity in the in-plane direction of the Si wafer.
- the film thickness of the Si oxide film 35 is controlled after forming the Si oxide film 35 with a predetermined thickness over the entire surface of the Si wafer 34 .
- the in-plane resistivity distribution of the Si wafer 34 is specified.
- the in-plane resistivity distribution of the Si wafer 34 for example, on the basis of the distribution of the resistivity in a radial direction of an ingot.
- the distribution of the resistivity in the radial direction of the ingot can be specified by calculating the distribution of the impurity concentration in the radial direction in each location in the lifting direction of the ingot as described above.
- the film thickness distribution of the Si oxide film 35 is measured in plane with the Si wafer 34 . Then, the film thickness of the Si oxide film 35 is controlled by trimming on the basis of the specified resistivity distribution and film thickness distribution, such that the piezo-resonator 13 has uniform frequency-temperature characteristics in plane with the Si wafer 34 .
- FIG. 10 is a diagram showing the relationship between the resistivity of a wafer and the frequency-temperature characteristics of the piezo-resonator 13 .
- the horizontal axis indicates the resistivity of a wafer
- the vertical axis indicates a primary coefficient term of frequency-temperature characteristics. From FIG. 10 , it is determined that as the resistivity of the wafer is increased, the frequency-temperature characteristics have a larger value, and approach asymptotically to around 2.0 ppm/K. Accordingly, from the relationship between the frequency-temperature characteristics and the resistivity, and the relationship between the frequency-temperature characteristic and the thickness of the Si oxide film as shown in FIG.
- the variation in frequency-temperature characteristics can be reduced by controlling the film thickness so as to make the Si oxide film 35 thinner, in a region where the resistivity is high in plane with the wafer.
- local etching with the use of, for example, a rare gas, for example, Ar (argon) ion beams, or a chemical reaction gas, for example, SF 6 (sulfur hexafluoride) gas plasma, or local etching of spraying a hydrofluoric acid solution from a thin nozzle to the Si wafer can be used for trimming the film thickness of the Si oxide film 35 .
- a rare gas for example, Ar (argon) ion beams
- a chemical reaction gas for example, SF 6 (sulfur hexafluoride) gas plasma
- spraying a hydrofluoric acid solution from a thin nozzle to the Si wafer can be used for trimming the film thickness of the Si oxide film 35 .
- This local etching makes it possible to reduce the variation in frequency-temperature characteristics on the basis of the resistivity in plane with the Si wafer.
- the manufacturing method described below may be implemented in place of the method for manufacturing a Cavity SOI as described above.
- the entire surface of the degenerated Si wafer 34 described previously is subjected to a thermal oxidation treatment, thereby forming the Si oxide film 35 with a predetermined thickness.
- a handle wafer 41 of Si is joined to the lower surface of the Si wafer 34 .
- a wafer 31 with a depression 33 is formed in the same way as described previously.
- the upper surface of the Si wafer 34 is bonded to the upper surface of the wafer 31 with the depression 33 by, for example, fusion joining.
- the handle wafer 41 is removed from the upper surface of the Si wafer 34 . Thereafter, as shown in FIG. 11( c ) , the Si oxide film 25 at the upper surface of the Si wafer 34 is removed by wet etching.
- a lower electrode film (for example, Mo) 36 , a piezoelectric thin film (for example, AlN) 37 , and an upper electrode film (for example, Mo) 38 are sequentially deposited on the upper surface of the Si wafer 34 , for example, by sputtering, thereby manufacturing a piezoelectric resonance device 10 .
- FIG. 12 is an exploded perspective view schematically illustrating a structure that represents the appearance of a piezoelectric resonance device 50 according to another exemplary aspect.
- This piezoelectric resonance device 50 includes a piezo-resonator 53 which oscillates in an in-plane spread oscillation mode, in place of the piezo-resonator 13 which oscillates in a flexural oscillation mode as described previously.
- the piezo-resonator 53 is sandwiched between a lower substrate 11 and an upper substrate 12 , as in the case of the piezo-resonator 13 described previously.
- the lower substrate 11 and the upper substrate 12 have the same configurations as the structures described previously, and the repeated explanations will be thus left out.
- the piezo-resonator 53 includes: a support frame 54 that spreads in the form of a rectangular frame along the XY plane in the orthogonal coordinate system in FIG. 12 ; an oscillation part 55 disposed inside the support frame 54 to spread in a rectangular form along the XY plane as in the case of the support frame 54 ; and a pair of connection parts 56 , 56 connecting the support frame 54 and the oscillation part 55 to each other.
- the oscillation part 55 oscillates by repeated stretching in the Y-axis direction along the XY plane, as will be described later.
- the support frame 54 includes: a pair of longer frame parts 54 a , 54 a extending parallel to the X axis; and a pair of shorter frame parts 54 b , 54 b extending parallel to the Y axis, with both ends thereof connected respectively to both ends of the frame parts 54 a , 54 a .
- the connection parts 56 , 56 extend in a straight line parallel to the X axis to connect the frame parts 54 b , 54 b and the oscillation part 55 to each other.
- the connection parts 56 , 56 are located at ends (node points) in intermediate positions of the oscillation part 55 in the Y-axis direction, that is, in center positions in the oscillation direction of the oscillation part 55 .
- FIG. 13 is a pattern diagram of a cross section along the line 12 - 12 of FIG. 12 .
- the support frame 54 , the oscillation part 55 , and the connection parts 56 are formed from: a Si oxide film, that is, a SiO 2 layer 61 ; an active film, that is, a Si layer 62 laminated on the SiO 2 layer 61 ; a piezoelectric thin film, that is, an AlN layer 63 laminated on the Si layer 62 ; a lower electrode, that is, a Mo layer 64 and an upper electrode, that is, a Mo layer 65 formed on the upper surface and lower surface of the AlN layer 63 to sandwich the AlN layer 63 therebetween; and further an AlN layer 63 ′ laminated on the Mo layer 65 .
- These layers have the same structures as the layers described previously, and the repeated explanations will be thus left out.
- the AlN layer 63 is C-axis oriented substantially perpendicular to the Si layer 62 .
- the oscillation part 55 is excited through the application of alternating electric field substantially in the C-axis direction between the Mo layer 64 and the Mo layer 65 .
- the oscillation part 55 undergoes stretching oscillation in the shorter side direction, that is, the Y-axis direction.
- the exemplary manufacturing method disclosed herein can be also applied to the piezoelectric resonance device 50 .
- the piezoelectric resonance devices 10 , 50 have been described to function as timing devices, the devices may be configured to function as, for example, a gyro sensor, an acceleration sensor, a pressure sensor, a microphone, an ultrasonic transducer, an energy harvester, or a RF (high-frequency) filter.
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Thermal Sciences (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
Description
- The present application is a continuation of PCT/JP2015/082672 filed Nov. 20, 2015, which claims priority to Japanese Patent Application No. 2014-265347, filed Dec. 26, 2014, the entire contents of each of which are incorporated herein by reference.
- The present disclosure relates to a method for manufacturing a resonator.
- Before resonators, such as piezo-resonators, are formed, ingots of Si (silicon) are manufactured that are doped with large amounts of impurities, such as n-type dopants like P (phosphorus), for example. Then, a plurality of wafers are cut out from these ingots, and resonators are formed in a plurality of zones defined on the wafers. Thereafter, the respective zones are cut along the outlines of the respective zones of the wafers to thereby form resonance devices.
- The ingots of Si are manufactured substantially in cylindrical shapes by the growth of single-crystalline Si according to, for example, a manufacturing method referred to as a CZ method (Czochralski method). For example, the ingots are manufactured by melting, on heating, polycrystalline Si doped with large amounts of n-type dopant, for example, such as P, and immersing Si rods in the molten Si, and lifting the Si rods while rotating the rods.
- Patent Document 1: Japanese Patent Application Laid-Open No. 2010-028536.
- It has been determined that these ingots each have a higher impurity concentration at the outer peripheral side in a radial direction of the ingot than at the inner peripheral side therein. At the same time, these ingots also have a higher impurity concentration at the bottom side in a lifting direction of the ingot than the top side therein. In accordance with these distributions in impurity concentration, the ingots each have a resistivity distribution formed to decrease in resistivity from the inner peripheral side toward the outer peripheral side, and a resistivity distribution formed to decrease in resistivity from the top side toward the bottom side.
- Moreover, when a plurality of wafers are cut out from the ingots that have such distributions in resistivity, the resistivity varies among the wafers, depending on the distributions in impurity concentration. When resonators are manufactured from these wafers, frequency temperature characteristics vary depending on the variation in resistivity among the wafers. However, conventionally, this variation in resistivity among wafers have not been addressed at all.
- The present disclosure provides a method for manufacturing a resonator that is capable of effectively addressing the variation in resistivity for each wafer.
- A method for manufacturing a resonator according to an exemplary aspect includes the step of forming a Si oxide film at the surface of a degenerated Si wafer, where the Si oxide film has a thickness set in accordance with the doping amount of impurity in the Si wafer.
- A method for manufacturing a resonator according to another exemplary aspect includes the step of forming a piezoelectric thin film on the surface of a degenerated Si wafer, where the piezoelectric thin film has a thickness set in accordance with the distribution of the doping amount of impurity in the Si wafer in an in-plane direction of thereof.
- A wafer body according to an exemplary aspect includes a degenerated Si wafer; and a piezoelectric thin film formed on the surface of the Si wafer, where the piezoelectric thin film has a thickness set in accordance with the distribution of the doping amount of impurity in the Si wafer in an in-plane direction of thereof.
- According to the present disclosure, a method for manufacturing a resonator can be provided that effectively addresses the variation in resistivity for each wafer.
-
FIG. 1 is a perspective view schematically illustrating the appearance of a piezoelectric resonance device according to an exemplary aspect. -
FIG. 2 is an exploded perspective view schematically illustrating the structure of a piezoelectric resonance device according to an exemplary aspect. -
FIG. 3 is a pattern diagram of a cross section of the piezo-resonator along the line 3-3 ofFIG. 2 . -
FIG. 4 is a graph showing the relationship between the thickness of a Si oxide film and the frequency-temperature characteristic range of a piezo-resonator. -
FIG. 5 is a graph showing the relationship between the thickness of a piezoelectric thin film and the frequency-temperature characteristic range of a piezo-resonator. -
FIG. 6 is a graph showing the relationship between the doping amount of impurity and the primary temperature coefficient of elastic constant of a piezo-resonator. -
FIGS. 7(a) to 7(c) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect. -
FIGS. 8(a) to 8(c) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect. -
FIGS. 9(a) and 9(b) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect. -
FIG. 10 is a graph showing the relationship between the resistivity of a wafer and the frequency-temperature characteristic range of a piezo-resonator. -
FIGS. 11(a) to 11(c) are each a pattern diagram of a cross section illustrating a method for manufacturing a piezoelectric resonance device according to an exemplary aspect. -
FIG. 12 is an exploded perspective view schematically illustrating the structure of a piezoelectric resonance device according to another exemplary aspect. -
FIG. 13 is a pattern diagram of a cross section of the piezo-resonator along the line 12-12 ofFIG. 12 . - An embodiment of the present disclosure will be described below with reference to the accompanying drawings.
FIG. 1 is a perspective view schematically illustrating the appearance of apiezoelectric resonance device 10 according to a specific example. As shown, thepiezoelectric resonance device 10 includes alower substrate 11, anupper substrate 12 that forms an oscillation space with thelower substrate 11, and a piezo-resonator 13 sandwiched between thelower substrate 11 and theupper substrate 12. In this example, the piezo-resonator 13 is a MEMS resonator manufactured by a MEMS technology that functions as, for example, a timing device incorporated in an electronic device such as a smartphone. -
FIG. 2 is an exploded perspective view schematically illustrating the structure of apiezoelectric resonance device 10 according to a specific example. As shown inFIG. 2 , the piezo-resonator 13 includes: asupport frame 14 that spreads in the form of a rectangular frame along the XY plane in the orthogonal coordinate system inFIG. 2 ; abase 15 that spreads in the form of a flat plate along the XY plane in thesupport frame 14 from one end of thesupport frame 14; and a plurality ofoscillation arms 16 that each extend along the XY plane from a fixed end connected to one end of thebase 15 toward a free end. According to the present embodiment, the fouroscillation arms 16 extend parallel to the Y axis. It is noted that the number ofoscillation arms 16 is not limited to 4, and can be, for example, any number of 3 or more according to alternative aspects. - For the
piezoelectric resonance device 10 according to an exemplary aspect, thelower substrate 11 spreads in the form of a plate along the XY plane, and the upper surface of the substrate has adepression 17 formed therein. Thedepression 17 formed in, for example, a flat cuboid shape forms a part of the oscillation space for theoscillation arms 16. On the other hand, theupper substrate 12 spreads in the form of a plate along the XY plane, and the lower surface of the substrate has adepression 18 formed therein. Thedepression 18 formed in, for example, a flat cuboid shape forms a part of the oscillation space for theoscillation arms 16. Thelower substrate 11 and theupper substrate 12 are both formed from Si (silicon). - In this
piezoelectric resonance device 10, thesupport frame 14 of the piezo-resonator 13 is received on a peripheral edge of the upper surface of thelower substrate 11, which is defined outside thedepression 17, and a periphery of the lower surface of theupper substrate 12, which is defined outside thedepression 18, is received on thesupport frame 14 of the piezo-resonator 13. In this way, the piezo-resonator 13 is held between thelower substrate 11 and theupper substrate 12, and thelower substrate 11, theupper substrate 12, and thesupport frame 14 of the piezo-resonator 13 form the oscillation space for theoscillation arms 16. This oscillation space is kept airtight, and the vacuum state is maintained. -
FIG. 3 is a pattern diagram of a cross section of the piezo-resonator 13 along the line 3-3 ofFIG. 2 . - Referring to
FIG. 3 together, in the case of the piezo-resonator 13, theoscillation arms 16 each includes: a Si oxide film (thermal oxidation film), for example, a SiO2 layer (silicon dioxide) 21; an active layer, that is, aSi layer 22 laminated on the SiO2 layer 21; a piezoelectric thin film, that is, an AlN (aluminum nitride)layer 23 laminated on theSi layer 22; a lower electrode, that is, a Mo (molybdenum)layer 24 and an upper electrode, that is, aMo layer 25 formed on the upper surface and lower surface of theAlN layer 23 to sandwich theAlN layer 23; and further, anAlN layer 23′ laminated on theMo layer 25. It is noted that the SiO2 layer 21 may be formed between theSi layer 22 and theMo layer 24, or on the upper surface of theMo layer 25. - A silicon oxide material including any composition of SiaOb layer (a and b are integers) is used for the Si oxide film. The active layer formed from a degenerated n-type Si semiconductor contains, as an impurity, that is, an n-type dopant, a
Group 15 element such as P (phosphorus), As (arsenic), and Sb (antimony). It is noted that two or more of P, As, and Sb may be mixed in the active layer. Furthermore, Ge (germanium) that has a larger ionic radius than the ionic radius of Si may be added to the active layer to control lattice distortion due to impurity doping in large amounts. According to the present embodiment, theSi layer 22 is doped with a predetermined doping amount of P (phosphorus) as an n-type dopant. - The
AlN layer 23 is a piezoelectric thin film that converts an applied voltage to oscillations. In place of theAlN layer 23, for example, a ScAlN (scandium-containing aluminum nitride) layer may be used for the piezoelectric thin film. In addition, in place of theAlN layer 23, a MgNbAlN (magnesium-niobium-containing aluminum nitride) layer, a MgZrAlN (magnesium-zirconium-containing aluminum nitride) layer, BAlN (boron-containing aluminum nitride), and GeAlN (germanium-containing aluminum nitride) may be used for the piezoelectric thin film. Furthermore, a GaN (gallium nitride) layer, an InN (indium nitride) layer, a ZnO (zinc oxide) layer, a PZT (lead zirconate titanate) layer, a KNN (potassium sodium niobate) layer, a LiTaO3 (lithium tantalate) layer, and a LiNbO3 (lithium niobate) layer may be used for the piezoelectric thin film. - In place of the Mo layers 24, 25, for example, a metal material such as Ru (ruthenium), Pt (platinum), Ti (titanium), Cr (chromium), Al (aluminum), Cu (copper), Ag (silver) or an alloy thereof is used for the lower electrode and the upper electrode. The
Mo layer 24 and theMo layer 25 are each connected to an alternating-current power supply (not shown) provided outside thepiezoelectric resonance device 10. For the connection, for example, an electrode (not shown) formed on the upper surface of theupper substrate 12, a through silicon via (TSV) (not shown) formed in thelower substrate 11 or theupper substrate 12, or the like is used. - The
AlN layer 23′ is, for example, a film for protecting theMo layer 25. It is noted that the layer formed on theMo layer 25 is not limited to the AlN layer, but may be, for example, a film formed from an insulator. - The
AlN layer 23 has a wurtzite structure, which is C-axis oriented substantially perpendicular to theSi layer 22. When a voltage is applied in the C-axis direction through theMo layer 24 and theMo layer 25, theAlN layer 23 is stretched in a direction substantially perpendicular to the C axis. With this stretching, theoscillation arms 16 undergo flexural displacement in the Z-axis direction to cause free ends thereof to undergo displacement toward the inner surfaces of thelower substrate 11 and theupper substrate 12, thereby oscillating in an out-of-plane flexural oscillation mode. - According to the present embodiment, the thicknesses of the Si oxide film and piezoelectric thin film are controlled in accordance with the doping amount of a dopant, that is, an impurity formed in an ingot in the manufacture of the ingot used for the manufacture of the piezo-
resonator 13, and the distribution of the doping amount. The control of the thicknesses of the Si oxide film and piezoelectric thin film can reduce variations in frequency-temperature characteristics of the piezo-resonator 13. Accordingly, as will be described below, the piezo-resonator 13 according to an exemplary aspect, that is, thepiezoelectric resonance device 10, can be provided which has favorable temperature characteristics. - Next, a method for setting the thicknesses of the Si oxide film and piezoelectric thin film will be described. Prior to the manufacture of the
piezoelectric resonance device 10, ingots in a substantially cylindrical shape are manufactured by, for example, a CZ method (Czochralski method). For each ingot, the doping amount of an impurity, for example, such as P is set to a predetermined setting. However, the ingots manufactured each have a tendency to have a higher impurity concentration at the outer peripheral side in a radial direction of the ingot than at the inner peripheral side therein, and have a higher impurity concentration at the bottom side in a lifting direction of the ingot than the top side therein. In this way, the distribution of the impurity concentration is produced in the ingots. - This distribution of the impurity concentration roughly agrees with the distribution of resistivity. Specifically, in accordance with the distribution of the impurity concentration in the lifting direction, the ingots each have such a resistivity distribution as a decrease in resistivity from the top side toward the bottom side. This resistivity distribution in the lifting direction can be specified by measuring the impurity concentration at a plurality of points in the ingot manufactured. For example, the resistivity distribution can be specified by measuring the impurity concentration through SIMS (secondary ion mass spectrometry) at a plurality of points at the bottom surface of a cylindrical block of ingot with ends removed from the ingot manufactured, and measuring the impurity concentration in the same way at a plurality of points at the upper surface of the cylindrical block. Alternatively, the resistivity may be actually measured at these points. The resistivity can be measured by, for example, a four probe method.
- In addition, in accordance with the distribution of the impurity concentration in the radial direction of the ingot, the ingots each have such a resistivity distribution as a decrease in resistivity from the inner peripheral side toward the outer peripheral side. This resistivity distribution in the radial direction can be specified by measuring the impurity concentration at a plurality of points in the radial direction at the bottom surface and upper surface of the cylindrical block of ingot, and in consideration of the distribution of the impurity concentration in the lifting direction, calculating the distribution of the impurity concentration in the radial direction in each position in the lifting direction of the ingot.
- Prior to the manufacture of the piezo-
resonator 13, a plurality of Si wafers are cut out from the cylindrical block of the ingot. Each Si wafer has an impurity concentration, that is, a resistivity in accordance with the location in the lifting direction in the ingot, and the wafers are sorted into respective lots grouped for each predetermined resistivity range. This operation of sorting into the lots is repeated for each ingot, thereby collecting, for each lot, a plurality of Si wafers with resistivity in a predetermined range, which are cut from a plurality of ingots. In this regard, the resistivity of the Si wafer as a criterion for sorting into the lots is specified on the basis of the average value for the doping amount of impurity (average value for resistivity) in the in-plane direction of the Si wafer. - The thickness of the Si oxide film, that is, the SiO2 layer 21 formed at the Si wafer is controlled, for example, in each lot unit. Thus, the frequency-temperature characteristic range of the piezo-
resonator 13 can be controlled appropriately in accordance with the distribution of the doping amount of impurity (resistivity) in the ingot in the lifting direction.FIG. 4 is a graph showing the relationship between the thickness of the Si oxide film and the frequency-temperature characteristic range of the piezo-resonator 13. The frequency-temperature characteristic range [ppm] refers to a value indicating a difference, that is, a magnitude of change between the maximum value and minimum value of the frequency in the operation temperature range (for example, −40° C. to 85° C.) of thepiezoelectric resonator 13. As this frequency-temperature characteristic range is smaller, the variation in frequency-temperature characteristics is reduced. - As is clear from
FIG. 4 , for example, when the doping amount of impurity in the Si wafer has an average value of 12.6×1019 atm/cm3, setting the thickness of the Si oxide film to 0.33 μm causes the frequency-temperature characteristic range to reach a minimum value. In addition, for example, when the doping amount of impurity in the Si wafer has an average value of 13.0×1019 atm/cm3, setting the thickness of the Si oxide film to 0.35 μm causes the frequency-temperature characteristic range to reach a minimum value. In this way, the variation in frequency-temperature characteristics is reduced by setting the thickness of the Si oxide film to a thickness that causes the frequency-temperature characteristic range to reach a minimum value. - In addition, in place of the thickness of the Si oxide film, that is, the SiO2 layer 21, or in addition to the thickness of the SiO2 layer 21, the thickness of the piezoelectric thin film that is, the
AlN film 23 may be controlled. For example, as in the case of the SiO2 layer 21, the thickness of theAlN film 23 is controlled in each lot unit. Thus, the frequency-temperature characteristic range of the piezo-resonator 13 can be controlled appropriately in accordance with the distribution of the doping amount of impurity (resistivity) in the ingot in a radial direction.FIG. 5 is a graph showing the relationship between the thickness of the piezoelectric thin film and the frequency-temperature characteristic range of the piezo-resonator 13. As in the case described previously, the frequency-temperature characteristic range [ppm] refers to a value indicating a difference, that is, a magnitude of change between the maximum value and minimum value of the frequency in the operation temperature range (for example, −40° C. to 85° C.) of thepiezoelectric resonator 13. - For example, a case is assumed where the doping amount of impurity is 1.26×1020 atm/cm3 near the center of the Si wafer, whereas the doping amount of impurity is 1.30×1020 atm/cm3 near the outer periphery of the Si wafer. In this case, as is clear from
FIG. 5 , near the center of the Si wafer, the thickness of the piezoelectric thin film is set to 0.850 μm with which the frequency-temperature characteristic range reaches a minimum value. In addition, near the outer periphery of the Si wafer, the thickness of the piezoelectric thin film is set to 0.790 μm with which the frequency-temperature characteristic range reaches a minimum value. - As described above, the distribution of the doping amount of impurity is formed in the in-plane direction of the Si wafer, and the thickness distribution is thus set in the radial direction in the case of the
AlN film 23 in accordance with the distribution of the doping amount, formed in the radial direction from the inner peripheral side of the Si wafer toward the outer peripheral side thereof, for example. This thickness distribution of the piezoelectric thin film in the radial direction is set so as to achieve a thickness distribution in which the frequency-temperature characteristic range reaches a minimum value, thereby reducing the variation in frequency-temperature characteristics. -
FIG. 6 is a graph showing the relationship between the doping amount of impurity and the primary temperature coefficient of elastic constant of the piezo-resonator 13. As is clear fromFIG. 6 , the frequency-temperature characteristics increase in a relatively rapid manner up to approximately 9×1019 atm/cm3 as the doping amount of impurity in the Si wafer is increased from 0, while the frequency-temperature characteristics decrease in relatively gradual manner when the doping amount of impurity exceeds approximately 9×1019 atm/cm3. - Therefore, in order to address the distribution of the doping amount (resistivity) in the in-plane direction of the Si wafer, for example, a material such as AlN or ScAlN that has a negative primary temperature coefficient of elastic constant is used as the piezoelectric thin film, and when the doping amount in the Si wafer is more than approximately 9×1019 atm/cm3, the thickness of the piezoelectric thin film is increased at the outer peripheral side of the Si wafer, rather than at the inner peripheral side thereof. On the other hand, in the case of the doping amount below approximately 9×1019 atm/cm3, the thickness of the piezoelectric thin film is decreased at the outer peripheral side of the Si wafer, rather than at the inner peripheral side thereof. More specifically, it is preferable to control the thickness distribution of the piezoelectric thin film, with the doping amount of approximately 9×1019 atm/cm3 as a threshold value.
- It is noted that the distribution of the doping amount (resistivity) in the in-plane direction of the Si wafer can be also addressed by control of the thickness distribution of the thin film (resonator-constituting thin film) constituting the piezo-
resonator 13 formed above theSi layer 22, in place of the control of the thickness distribution of the piezoelectric thin film. Examples of the resonator-constituting thin film include, for example, thelower electrode 24 and theupper electrode 25. Besides, the distribution of the doping amount (resistivity) in the in-plane direction of the Si wafer can be also addressed by control of the distribution of, for example, the thickness of a parasitic capacitance-reducing (for example, silicon oxide) layer formed between thelower electrode 24 and theSi layer 22, or the thickness of an additional thin film layer such as a protective film layer of, for example, a silicon oxide layer or an AlN layer formed on theupper electrode 25. - For the foregoing resonator-constituting thin film, in the case of using, as the resonator-constituting thin film, a material such as, for example, AlN, Mo, Al, Pt, Ru, Ir (iridium), Ti, ScAlN, or SiN (silicon nitride) that has a negative primary temperature coefficient of elastic constant, it is preferable to control the thickness distribution of the resonator-constituting thin film, with the doping amount of approximately 9×1019 atm/cm3 as a threshold value in the same way as described previously. The distribution of the thickness in the in-plane direction of the Si wafer is controlled in the same way as described previously. It is noted that in the case of, for example, a material that has a positive primary temperature coefficient of elastic constant, such as SiO2 or SiOF (fluorine-containing silicon oxide film), it is preferable to set the thickness in an opposite manner to the foregoing in the in-plane direction of the Si wafer, with the above-mentioned threshold voltage as a boundary.
- Next, a method for manufacturing the
piezoelectric resonance device 10 will be schematically described below.FIGS. 7(a) to 7(c) are each a cross-sectional view for explaining a method for manufacturing thepiezoelectric resonance device 10 according to an exemplary aspect. It is noted that while a plurality of zones corresponding to respectivepiezoelectric resonance devices 10 are defined on a Si wafer, only one zone on the Si wafer is illustrated in the figures for the following explanation of the manufacturing method. In addition, the thicknesses of the Si oxide film and piezoelectric thin film are controlled for each lot of a plurality of collected Si wafers with a predetermined range of resistivity. - First, as shown in
FIG. 7(a) , for the manufacture of thelower substrate 11, a plate-like wafer 31 formed from Si is prepared, and the entire surface of thewafer 31 is subjected to a thermal oxidation treatment, thereby forming a Si oxide film (for example, SiO2) 32 with a predetermined thickness over the entire surface of thewafer 31. As shown inFIG. 7(b) , in the surface of thewafer 31, adepression 33 is formed by, for example, etching. Thereafter, as shown inFIG. 7(c) , thewafer 31 is cleaned after removing theSi oxide film 32. In this way, thelower substrate 11 with thedepression 17 in the upper surface thereof is formed. - On the other hand, as shown in
FIG. 8(a) , for the manufacture of the piezo-resonator 13, a degeneratedSi wafer 34 is prepared. TheSi wafer 34 is doped with an impurity in a predetermined doping amount, the actual doping amount (resistivity) of theSi wafer 34 is specified in advance. The entire surface of theSi wafer 34 is subjected to a thermal oxidation treatment, thereby forming a Si oxide film (for example, SiO2) 35 with a predetermined thickness. It is noted that besides thermal oxidation films, TEOS oxidation films, PECVD oxidation films, and sputtered oxidation films can be used for theSi oxide film 35. The thickness of the Si oxide film is set in accordance with the average value for the actual doping amount (resistivity) in the in-plane direction of theSi wafer 34 as described above. - Thereafter, as shown in
FIG. 8(b) , the lower surface of theSi wafer 34 is put on the upper surface of thewafer 31 described previously, thereby joining theSi wafer 34 to the upper surface of thewafer 31. For the joining, for example, fusion joining is carried out. Subsequently, as shown inFIG. 8(c) , the upper surface of theSi wafer 34 is subjected to a grinding treatment and a polishing treatment (CMP: chemical mechanical polishing), thereby grinding and removing theSi oxide film 35 at the upper surface of theSi wafer 34 and a part of theSi wafer 34, and thus planarizing the surface of theSi wafer 34. In this way, a so-called Cavity SOI is manufactured. - Thereafter, as shown in
FIG. 9(a) , on theSi wafer 34, a lower electrode film (for example, Mo) 36, a piezoelectric thin film (for example, AlN) 37, an upper electrode film (for example, Mo) 38, and a piezoelectricthin film 37′ are sequentially deposited by, for example, sputtering. In this regard, the thickness of the piezoelectricthin film 37 is set in accordance with the distribution of the doping amount of impurity (resistivity) in the in-plane direction of theSi wafer 34 as described above. For example, the thickness of the piezoelectricthin film 37 has a distribution in the in-plane direction such that the thickness of the piezoelectricthin film 37 is decreased from near the center of theSi wafer 34 toward the outer periphery. In this way, a wafer body is manufactured which includes the piezoelectricthin film 37 with a thickness set in accordance with the distribution of the doping amount (resistivity) in the in-plane direction of theSi wafer 34. - In this regard, for the formation of the piezoelectric
thin film 37, for example, an Al target (not shown) is disposed to be opposed to the upper surface of theSi wafer 34. A magnet (not shown) is disposed behind the Al target to confine electrons in a magnetic field, thereby accelerating ionization of an inert gas such as Ar (argon), and thus generating a high concentration of plasma around the Al target. As a result, the piezoelectricthin film 37 can be deposited at high speed. Accordingly, the distribution of sputtered particles that reach the upper surface of theSi wafer 34 depends largely on the distribution of the magnetic field formed by the magnet. In other words, controlling the distribution of the magnetic field allows the thickness of the piezoelectricthin film 37 to have a distribution. - Accordingly, for example, the location of the magnet or the rotation speed of the
Si wafer 34 is adjusted to control the magnetic field intensity of the magnet, thereby allowing the thickness of the piezoelectricthin film 37 to have a distribution in the in-plane direction. Alternatively, in place of this method, it is also possible to measure the thickness of the piezoelectricthin film 37 actually after forming the piezoelectricthin film 37 with a uniform thickness on the upper surface of theSi wafer 34, and chip away the piezoelectricthin film 37 with Ar ion beams or the like so as to achieve a desired distribution in thickness, thereby causing the piezoelectricthin film 37 to have a distribution in thickness. According to this method, the thickness of the piezoelectricthin film 37 can be controlled in a more precise manner. - Subsequently, as shown in
FIG. 9(b) , theSi wafer 34, theSi oxide film 35, thelower electrode film 36, the piezoelectricthin film 37, theupper electrode film 38, and the piezoelectricthin film 37′ are subjected to, for example, dry etching or wet etching, thereby forming the shapes of thesupport frame 14,base 15, andoscillation arms 16 described above. In this way, the piezo-resonator 13 is formed which is supported by thesupport frame 14 on the upper surface of thelower substrate 11. Thereafter, a wafer (not shown) that has depressions formed in advance in zones corresponding to the respective zones of theSi wafer 34 is joined onto the piezo-resonator 13. Subsequently, respectivepiezoelectric resonance devices 10 are cut out along the outlines of the respective zones, for example, with a diamond blade or by a laser dicing method. - It is noted that while the both thicknesses of the
Si oxide film 35 and piezoelectricthin film 37 are controlled in accordance with the doping amount of impurity (resistivity) in the degeneratedSi wafer 34 and the distribution thereof according to the above-described method for manufacturing thepiezoelectric resonance device 10, the exemplary embodiments are not to be considered limited thereto, but for example, the thickness of only either theSi oxide film 35 or the piezoelectricthin film 37 may be controlled. Preferably, thepiezoelectric resonance device 10 which varies little in frequency-temperature coefficient can be provided even by controlling the thickness of only either theSi oxide film 35 or the piezoelectricthin film 37 in this way as just described. - Moreover, a method where a Si wafer is sorted into a lot on the basis of the average value for the doping amount of impurity in the in-plane direction of the Si wafer, and the thickness of the SiO2 layer 21 formed at the Si wafer is controlled in each lot unit has been described as an example in accordance with the above-described method for manufacturing the
piezoelectric resonance device 10. However, the exemplary embodiment should not be limited thereto and it is also possible to further control the thickness of the SiO2 layer 21 in accordance with the distribution of the doping amount of impurity in the in-plane direction of the Si wafer. - Specifically, in the step shown in
FIG. 8(a) , the film thickness of theSi oxide film 35 is controlled after forming theSi oxide film 35 with a predetermined thickness over the entire surface of theSi wafer 34. Prior to the control of the film thickness of theSi oxide film 35, first, the in-plane resistivity distribution of theSi wafer 34 is specified. - It is possible to specify the in-plane resistivity distribution of the
Si wafer 34, for example, on the basis of the distribution of the resistivity in a radial direction of an ingot. Specifically, the distribution of the resistivity in the radial direction of the ingot can be specified by calculating the distribution of the impurity concentration in the radial direction in each location in the lifting direction of the ingot as described above. - Next, the film thickness distribution of the
Si oxide film 35 is measured in plane with theSi wafer 34. Then, the film thickness of theSi oxide film 35 is controlled by trimming on the basis of the specified resistivity distribution and film thickness distribution, such that the piezo-resonator 13 has uniform frequency-temperature characteristics in plane with theSi wafer 34. -
FIG. 10 is a diagram showing the relationship between the resistivity of a wafer and the frequency-temperature characteristics of the piezo-resonator 13. InFIG. 10 , the horizontal axis indicates the resistivity of a wafer, whereas the vertical axis indicates a primary coefficient term of frequency-temperature characteristics. FromFIG. 10 , it is determined that as the resistivity of the wafer is increased, the frequency-temperature characteristics have a larger value, and approach asymptotically to around 2.0 ppm/K. Accordingly, from the relationship between the frequency-temperature characteristics and the resistivity, and the relationship between the frequency-temperature characteristic and the thickness of the Si oxide film as shown inFIG. 4 , it is determined that for example, in the case of a wafer of 0.5 mΩcm in average resistivity, the variation in frequency-temperature characteristics can be reduced by controlling the film thickness so as to make theSi oxide film 35 thinner, in a region where the resistivity is high in plane with the wafer. - For example, local etching with the use of, for example, a rare gas, for example, Ar (argon) ion beams, or a chemical reaction gas, for example, SF6 (sulfur hexafluoride) gas plasma, or local etching of spraying a hydrofluoric acid solution from a thin nozzle to the Si wafer can be used for trimming the film thickness of the
Si oxide film 35. - This local etching makes it possible to reduce the variation in frequency-temperature characteristics on the basis of the resistivity in plane with the Si wafer.
- In addition, the manufacturing method described below may be implemented in place of the method for manufacturing a Cavity SOI as described above. For example, as shown in
FIG. 11(a) , the entire surface of the degeneratedSi wafer 34 described previously is subjected to a thermal oxidation treatment, thereby forming theSi oxide film 35 with a predetermined thickness. Ahandle wafer 41 of Si is joined to the lower surface of theSi wafer 34. On the other hand, awafer 31 with adepression 33 is formed in the same way as described previously. Thereafter, as shown inFIG. 11(b) , the upper surface of theSi wafer 34 is bonded to the upper surface of thewafer 31 with thedepression 33 by, for example, fusion joining. - After joining the
wafer 31 and theSi wafer 34, thehandle wafer 41 is removed from the upper surface of theSi wafer 34. Thereafter, as shown inFIG. 11(c) , theSi oxide film 25 at the upper surface of theSi wafer 34 is removed by wet etching. - Thereafter, in the same way as described previously, a lower electrode film (for example, Mo) 36, a piezoelectric thin film (for example, AlN) 37, and an upper electrode film (for example, Mo) 38 are sequentially deposited on the upper surface of the
Si wafer 34, for example, by sputtering, thereby manufacturing apiezoelectric resonance device 10. -
FIG. 12 is an exploded perspective view schematically illustrating a structure that represents the appearance of apiezoelectric resonance device 50 according to another exemplary aspect. Thispiezoelectric resonance device 50 includes a piezo-resonator 53 which oscillates in an in-plane spread oscillation mode, in place of the piezo-resonator 13 which oscillates in a flexural oscillation mode as described previously. The piezo-resonator 53 is sandwiched between alower substrate 11 and anupper substrate 12, as in the case of the piezo-resonator 13 described previously. Thelower substrate 11 and theupper substrate 12 have the same configurations as the structures described previously, and the repeated explanations will be thus left out. - The piezo-
resonator 53 includes: asupport frame 54 that spreads in the form of a rectangular frame along the XY plane in the orthogonal coordinate system inFIG. 12 ; anoscillation part 55 disposed inside thesupport frame 54 to spread in a rectangular form along the XY plane as in the case of thesupport frame 54; and a pair ofconnection parts support frame 54 and theoscillation part 55 to each other. Theoscillation part 55 oscillates by repeated stretching in the Y-axis direction along the XY plane, as will be described later. - The
support frame 54 includes: a pair oflonger frame parts shorter frame parts frame parts connection parts frame parts oscillation part 55 to each other. Theconnection parts oscillation part 55 in the Y-axis direction, that is, in center positions in the oscillation direction of theoscillation part 55. -
FIG. 13 is a pattern diagram of a cross section along the line 12-12 ofFIG. 12 . As is clear fromFIG. 13 , in the case of piezo-resonator 53, thesupport frame 54, theoscillation part 55, and theconnection parts 56 are formed from: a Si oxide film, that is, a SiO2 layer 61; an active film, that is, aSi layer 62 laminated on the SiO2 layer 61; a piezoelectric thin film, that is, anAlN layer 63 laminated on theSi layer 62; a lower electrode, that is, aMo layer 64 and an upper electrode, that is, aMo layer 65 formed on the upper surface and lower surface of theAlN layer 63 to sandwich theAlN layer 63 therebetween; and further anAlN layer 63′ laminated on theMo layer 65. These layers have the same structures as the layers described previously, and the repeated explanations will be thus left out. - In this
piezoelectric resonance device 50, theAlN layer 63 is C-axis oriented substantially perpendicular to theSi layer 62. Theoscillation part 55 is excited through the application of alternating electric field substantially in the C-axis direction between theMo layer 64 and theMo layer 65. As a result, theoscillation part 55 undergoes stretching oscillation in the shorter side direction, that is, the Y-axis direction. In other words, there is stretching oscillation of repeating the stretchedoscillation part 55 and the shortenedoscillation part 55 in the Y-axis direction. It should be appreciated that the exemplary manufacturing method disclosed herein can be also applied to thepiezoelectric resonance device 50. - While the
piezoelectric resonance devices - It is noted that the foregoing respective embodiments are intended to facilitate understanding of the present disclosure, but not intended to construe the exemplary embodiments in any limited way. Modifications and/or improvements can be made without departing from the spirit of the invention, and the exemplary embodiments encompass equivalents thereof. More specifically, the scope of the present disclosure also encompasses therein the respective embodiments with design changes appropriately made thereto by one skilled in the art. For example, the respective elements included in the respective embodiments, and the layout, materials, conditions, shapes, sizes, and the like of the elements are not to be considered limited to those exemplified, but may be changed appropriately. In addition, the respective elements included in the respective elements may be combined as long as the combinations are technically possible, and the scope of the present disclosure also encompasses therein the combinations as long as the combinations have the features of the present disclosure.
-
-
- 13: resonator (piezo-resonator)
- 21: Si oxide film
- 23: piezoelectric thin film
- 34: Si wafer
- 35: Si oxide film
- 37: piezoelectric thin film
- 53: resonator (piezo-resonator)
- 61: Si oxide film
- 63: piezoelectric thin film
Claims (17)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2014-265347 | 2014-12-26 | ||
JP2014265347 | 2014-12-26 | ||
PCT/JP2015/082672 WO2016104004A1 (en) | 2014-12-26 | 2015-11-20 | Resonator manufacturing method |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2015/082672 Continuation WO2016104004A1 (en) | 2014-12-26 | 2015-11-20 | Resonator manufacturing method |
Publications (2)
Publication Number | Publication Date |
---|---|
US20170272050A1 true US20170272050A1 (en) | 2017-09-21 |
US10727807B2 US10727807B2 (en) | 2020-07-28 |
Family
ID=56150037
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US15/610,896 Active 2037-01-12 US10727807B2 (en) | 2014-12-26 | 2017-06-01 | Resonator manufacturing method |
Country Status (5)
Country | Link |
---|---|
US (1) | US10727807B2 (en) |
JP (1) | JP6395008B2 (en) |
CN (1) | CN107112967B (en) |
SG (1) | SG11201705232YA (en) |
WO (1) | WO2016104004A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10191571B2 (en) * | 2016-07-22 | 2019-01-29 | Boe Technology Group Co., Ltd. | Substrate and display device |
US10291202B2 (en) * | 2013-09-20 | 2019-05-14 | Murata Manufacturing Co., Ltd. | Vibration device and manufacturing method of the same |
US10339776B2 (en) * | 2017-11-14 | 2019-07-02 | Sensormatic Electronics Llc | Security marker |
US10397708B2 (en) | 2015-12-02 | 2019-08-27 | Murata Manufacturing Co., Ltd. | Piezoelectric element, piezoelectric microphone, piezoelectric resonator and method for manufacturing piezoelectric element |
US20230022989A1 (en) * | 2021-07-20 | 2023-01-26 | Sonicmems (Zhengzhou) Technology Co., Ltd. | Suspended piezoelectric ultrasonic transducer and manufacturing thereof |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP7097074B2 (en) * | 2019-02-07 | 2022-07-07 | 国立研究開発法人産業技術総合研究所 | Nitride piezoelectric material and MEMS device using it |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2756476B2 (en) * | 1989-04-17 | 1998-05-25 | 住友シチックス株式会社 | Method for producing p-type silicon single crystal |
JP2001168675A (en) * | 1999-12-08 | 2001-06-22 | Mitsubishi Electric Corp | Piezoelectric resonator, piezoelectric oscillator using this and method for manufacturing piezoelectric resonator |
JP2005236337A (en) | 2001-05-11 | 2005-09-02 | Ube Ind Ltd | Thin-film acoustic resonator and method of producing the same |
JP2005236338A (en) * | 2001-05-11 | 2005-09-02 | Ube Ind Ltd | Piezoelectric thin-film resonator |
CN100527615C (en) * | 2004-04-20 | 2009-08-12 | 株式会社东芝 | Film bulk acoustic-wave resonator and method for manufacturing the same |
JP2007019758A (en) * | 2005-07-06 | 2007-01-25 | Toshiba Corp | Thin film piezo-electricity resonant element and manufacturing method thereof |
JP5316748B2 (en) * | 2008-03-28 | 2013-10-16 | セイコーエプソン株式会社 | Manufacturing method of vibrating piece |
JP5168002B2 (en) | 2008-07-22 | 2013-03-21 | セイコーエプソン株式会社 | Vibrator and oscillator |
WO2014185280A1 (en) * | 2013-05-13 | 2014-11-20 | 株式会社村田製作所 | Vibrating device |
-
2015
- 2015-11-20 JP JP2016566041A patent/JP6395008B2/en active Active
- 2015-11-20 CN CN201580070969.9A patent/CN107112967B/en active Active
- 2015-11-20 SG SG11201705232YA patent/SG11201705232YA/en unknown
- 2015-11-20 WO PCT/JP2015/082672 patent/WO2016104004A1/en active Application Filing
-
2017
- 2017-06-01 US US15/610,896 patent/US10727807B2/en active Active
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10291202B2 (en) * | 2013-09-20 | 2019-05-14 | Murata Manufacturing Co., Ltd. | Vibration device and manufacturing method of the same |
US10397708B2 (en) | 2015-12-02 | 2019-08-27 | Murata Manufacturing Co., Ltd. | Piezoelectric element, piezoelectric microphone, piezoelectric resonator and method for manufacturing piezoelectric element |
US11012787B2 (en) | 2015-12-02 | 2021-05-18 | Murata Manufacturing Co., Ltd. | Piezoelectric element, piezoelectric microphone, piezoelectric resonator and method for manufacturing piezoelectric element |
US10191571B2 (en) * | 2016-07-22 | 2019-01-29 | Boe Technology Group Co., Ltd. | Substrate and display device |
US10339776B2 (en) * | 2017-11-14 | 2019-07-02 | Sensormatic Electronics Llc | Security marker |
US20230022989A1 (en) * | 2021-07-20 | 2023-01-26 | Sonicmems (Zhengzhou) Technology Co., Ltd. | Suspended piezoelectric ultrasonic transducer and manufacturing thereof |
Also Published As
Publication number | Publication date |
---|---|
JPWO2016104004A1 (en) | 2017-08-31 |
CN107112967B (en) | 2020-07-07 |
SG11201705232YA (en) | 2017-07-28 |
WO2016104004A1 (en) | 2016-06-30 |
CN107112967A (en) | 2017-08-29 |
US10727807B2 (en) | 2020-07-28 |
JP6395008B2 (en) | 2018-09-26 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US10727807B2 (en) | Resonator manufacturing method | |
US10291202B2 (en) | Vibration device and manufacturing method of the same | |
JP3940932B2 (en) | Thin film piezoelectric resonator, thin film piezoelectric device and manufacturing method thereof | |
US10553778B2 (en) | Piezoelectric device and method for manufacturing piezoelectric device | |
US10432162B2 (en) | Acoustic resonator including monolithic piezoelectric layer having opposite polarities | |
JP6756991B2 (en) | Piezoelectric MEMS resonator with high Q value | |
CN113285687B (en) | Temperature compensation type film bulk acoustic resonator, forming method thereof and electronic equipment | |
JP2003110388A (en) | Piezoelectric oscillator element and manufacturing method thereof, and piezoelectric device | |
WO2019185324A1 (en) | Bulk acoustic wave resonator device and method of manufacturing thereof | |
CN111108690A (en) | Resonator and resonance device | |
CN112534719A (en) | Resonance device | |
CN110741550A (en) | Resonator and resonance device | |
WO2013031650A1 (en) | Elastic wave device and production method therefor | |
WO2020070942A1 (en) | Resonator and resonance device | |
JPWO2020085188A1 (en) | Resonator | |
CN111989863A (en) | Resonator and resonance device | |
WO2019228750A1 (en) | Method of manufacturing a bulk acoustic wave resonator and bulk acoustic wave resonator device | |
KR102313290B1 (en) | Film bulk acoustic resonator and method for fabricating the same | |
WO2022130676A1 (en) | Resonator and resonating device | |
CN205792476U (en) | A kind of FBAR using ultra-thin piezoelectric single crystal to make | |
JP5839997B2 (en) | Manufacturing method of crystal unit | |
JP2003060481A (en) | Piezoelectric oscillation element and manufacturing method therefor, and piezoelectric device | |
US20240128948A1 (en) | Resonance device and method for manufacturing same | |
Nestler et al. | Yield improvement by localized trimming in semiconductor and MEMS manufacturing | |
JP3939991B2 (en) | Piezoelectric resonator and piezoelectric resonator |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: MURATA MANUFACTURING CO., LTD., JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:UMEDA, KEIICHI;YAMADA, HIROSHI;AIDA, YASUHIRO;SIGNING DATES FROM 20170526 TO 20170529;REEL/FRAME:042567/0257 |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: PUBLICATIONS -- ISSUE FEE PAYMENT VERIFIED |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Year of fee payment: 4 |